Bricks have been made from clay or from concrete. A brick made from clay may be made by molding a clay containing material into the shape of a brick having sufficient green strength to be capable of being removed from a mold. The green strength of the molded, brick-shaped clay is also sufficient to allow the molded clay to hold its shape during subsequent handling and treatment after being removed from the mold. The molded, brick-shaped clay is then placed in a kiln and heated to extremely high temperatures to harden the clay into a brick of sufficient strength to be used as a building material.
A brick made from concrete may be made by an entirely different process. The formation of concrete requires two components, i.e. a cement composition and water. A dry cement composition typically includes a mixture of a powdery, dry cement and a filler, such as sand and gravel. The dry cement composition may be combined with water to form a pourable aqueous mixture of water and solid. This pourable mixture may be poured into a mold. In the mold, the cement composition hardens to form a concrete brick material. When the concrete brick material is sufficiently cured to be removed from the mold, while retaining its shape, it may be removed from the mold and may continue to harden over time. The hardening or curing of the cement into concrete takes place by virtue of a chemical reaction of the cement with water, and this curing may take place under ambient conditions without heating of the material. Bricks formed from cement have a disadvantage in that, for example, they tend to be heavy, brittle and lack thermal insulation properties.
Handling of cement in large quantities, particularly in brick formation, also has an environmental disadvantage, in terms of generation of solid fines in the air. In particular, cement includes solid fines, which can be caught up in the air when the cement is moved or handled in the open atmosphere. The amount of fines introduced into the atmosphere is proportional to the amount of cement which is processed.
As noted above, in addition to environmental concerns attributed to the generation of atmospheric fines, manufacture of bricks from cement tends to produce heavy bricks. In order to reduce the weight of bricks, light weight plastic material has been used as a filler in the cement composition used to form the bricks.
The Shulman U.S. Pat. No. 5,580,378 describes a dry, cement-containing composition including, for example, fly ash, Portland cement, sand, lime and a weight saving component, which is micronized (e.g., very small particle size) polystyrene. The dry cement-containing composition may be mixed with water, placed in a mold as a liquid cement and used to make bricks. In this molding process, no heat or pressure to compress the molded cement is needed or desired.
The Malloy et al U.S. Pat. No. 6,669,773 describes a cement-containing composition including Portland cement. A blend of fly ash with at least two plastic materials is included as a filler or “aggregate,” for the cement-containing composition. Examples of the plastic used in the blend include polyethylene terephthalate (PET) and high density polyethylene (HDPE). The cement-containing composition may be mixed with water, placed in a mold as a liquid cement and used to make bricks. In this molding process, no heat or pressure to compress the molded cement is needed or desired.
With the increase in the amount of plastic waste produced on a daily basis, modern communities need to provide practical and strategic ways to recycle such materials. There are several methods for dealing with plastic waste. One method involves a chemical recycle process to produce valuable gasses and liquid hydrocarbons. However, in order to achieve this goal, chemicals and special equipment have to be used, which make chemical recycling not desirable. Physical or material recycling, where plastic waste is re-melted and pelletized, offers a cost-effective method to make use of waste plastic. However, care needs to be taken to make sure that impurities are not present in the articles being recycled. Another drawback related to material recycling is that the application for the recycled articles has to be for the long term. Otherwise, plastic waste will need to be recycled again. For example, PET from bottles may be recycled to produce further PET bottles, but this short term type of recycling tends to generate further waste PET at the same rate that it is recycled.
High density polyethylene (HDPE) is a very common plastic used in making containers, such as milk jugs, shampoo bottles, water jugs, juice containers and soft drink bottles. There is a particular need to recycle post consumer HDPE from such discarded containers.